Search of the chemical change of the119mSn (T1/2=293 days) radioactive decay rate

The differences in decay rates of the nuclear isomer^119mSn (T_1/2=293 days; the strongly converted M4 transition) have been measured for different chemical compounds. The experimental results show that the^119mSn nuclei in the telluride SnTe decay faster then in the metal -Sn and in the dioxide SnO₂ the relative change / of the decay probability is +(3.6±1.4)·10^–4]. No measurable difference between the decay rates of^119mSn in -Sn and SnO₂ has been observed (/=–(0.1±1.2)·10^–4], irrespective of the great difference in electronic structure of the tin atoms. The results cannot be explained by considering the internal conversion of the valence electrons only. It is necessary to assume that the chemical changes of the decay rate are strongly influenced by the chemical changes of the probabilities of the internal conversion of electrons of the inner shells of the atom. This conclusion is confirmed by theoretical calculations. They show that for the deep inner subshells the relative changes _nlj/_nlj of the internal conversion coefficients _nlj are much greater than the relative changes _nlj/_nlj of the electron densities near the nucleus _nlj.